Small mammals on unpaved banks of canalized watersheds were studied in the agrocenosis of E Bohemia. A total of 13 species were caught. Diversity was high (total range 2.8-2.53, mean value H 2.31) compared with those from fields and scattered greenery. The communities were characterized by a concentration of a small number of species (Microtus arvalis, Apodemus sylvaticus, Sorex araneus), which represented >3/4 of the material. Late summer and autumn immigrations of field rodent species (M. arvalis, A. sylvaticus) from adjoining fields substantially influence the structure of the communities. There existed the clear decreasing gradient of the species diversity within the stream bank profile in a direction from lower to upper parts of a corridor. Canalization of the streams in agrocenosis is accompanied mainly by decrease of the diversity and by increase of dominance of rodents to the detriment of insectivores (Sorex araneus, Neomys fodiens).